Mine fuze



June 21, 1960 i R. E. LEE ETAL 2,941,472

- MINE FUZE Filed Au 10, 1956 23 INVENTORS 3 [a g 25 30 Robert E- LEE 2 l9 20 duhn H. ME Ivor ATTORNEYfi United States Patent MINE FUZE Robert E. Lee and John H. Mclvor, Denville, NJ., as-

signors to the United States of America as represented by the Secretary of the Army Filed Aug. 10, 1956, Ser. No. 603,454

Claims. (Cl. 102-70) (Granted under Title 35, US. Code (1952), see. 266) The invention described in the specification and claims may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a fuze for detonating land mines and can be manufactured in suitable size to set off anti-tank or anti-personnel mines.

An object of the invention is to provide a fuze in which the firing pin spring is unstressed in normal position of the fuze assembly, and stressed and fired only when the assembly is fully depressed.

Another object of the invention-is to provide a fuze having safety means whereby the fuze setting can be changed from safe to armed position at will without removing the fuze or mine from the ground after plant- 1ng.

A further object of the invention is to provide a fuze in which the firing assembly, in safe position, can be fully depressed without firing and will return to normal position when the load is removed.

Other objects and advantages will be apparent from the following detailed description and the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional view of a preferred form of the invention in normal armed position;

Fig. 2 is a transverse sectional view taken on the line 22 of Fig. 1, looking in the direction of the arrows, to disclose the means whereby the fuze setting is changed from normal armed to safe position; and

Fig. 3 is a View similar to Fig. 1 with the fuze assembly in fully depressed and fired position.

Armed position of the fuze will be hereinafter referred to as normal position, because the firing pin is not cocked until later as will hereinafter be explained.

Referring to the drawings, the fuze assembly is housed in a hollow cylindrical casing 1 having a longitudinal axis XX. External screw-threads 2 are formed on the lower end of the casing for connection with any standard type of land mine, a portion of which is indicated at 3. A closure plate 4 is secured in the lower end of casing 1 by any preferred means, such as the screwthreaded connection 5, and carries a standard primer 6. At its upper end the casing 1 is provided with stop means, in the present illustration shown as an upwardly converging inner wall 7. Fitted to abut the wall 7, is a frusto-conical presser member 8, held against accidental displacement by a frangible ring 9, and sealed against entrance of moisture by a packing ring 10.

Housed within the casing 1 intermediately of the closure plate 4 and the presser member 8 is a firing assembly 11 in which a firing pin retainer 12 is resiliently held by a first helical spring 13 seated in circular spring seats 14 and 15 in the abutting faces of the closure plate 4 and the firing pin retainer 12, respectively. The firing pin retainer has a diametrically reduced portion forming a flange 16, between which and the lower surface of the presser member, a second helical spring 17 is positioned.

2,941,472 Patented June 21, 1960 The two springs, 13 and 17, combine their thrust to hold the firing pin retainer and the presser member in normal position, see Fig. 1.

An axial bore 18 is formed in the firing pin retainer 12, open at its upper end and closed at its lower end by a web 19 in which an aperture 20 is formed. A cap member 21 is slidable in the bore 18 and abuts the lower surface of the presser member 8. Coaxially of the cap member a bore 22 and a counterbore 23 are formed to slidably receive a firing pin 24 and a firing pin spring 25, respectively. At its lower end the firing pin carries a diametrically enlarged head 26 on which the unstressed firing pin spring rests.

A recess 27 is formed in the firing pin retainer adjacent to and communicating with the bore 18, in which a sear 28 rotates about a pivot pin 29. The lower end of the sear is formed with a notch 30 which supports the enlarged head 26 of the firing pin, and a cam surface 31 in the path of movement of the lower end of the cap member supports the cap in normal position. A sear spring 32 is seated in a depression in the outer wall of the recess 27 and urges the cam surface of the sear into engagement with the lower end of the cap member 21. The upper end of the sear is reduced in width to form a tang 33 which extends upwardly into a groove 34 in the bottom face of the presser member. The groove is substantially L-shaped and has one leg 35 extending radially and in normal position the tang 33 is free to rotate about its pivot element 29. The other leg 36 of the groove 34 is concentric with the axis XX and in communication with the leg 35 of the L-shaped groove 34 and in arcuate alignment with the tang in normal position. It is therefor apparent that by applying a spanner wrench to the presser member, clockwise rotation thereof will rotate the groove leg 36 to embrace the tank 33 and prevent the sear from rotating and releasing the firing pin, when the fuze is in safe position.

The operation is as follows:

When the wheel of a vehicle, or other object bears on the presser member 8, the presser member, the second spring 17 and the entire firing assembly 17 descends from the position in Fig. 1, compressing the first spring 13 which is of lesser strength than the second spring 17. This downward movement of the presser member and the firing assembly causes the firing pin retainer 12 to abut the closure plate 4 whereupon the second spring 17 is compressed to the position in Fig. 3, lowering the presser member relative to the firing pin retainer. During this last part of the movement of the presser member, the cap member 21 is depressed to stress the firing pin spring 25 against the head 26 of the firing pin and finally cam the lower end of the sear 28 outwardly to release the head 26 of the firing pin from the notch 30 and detonate the primer. When the sear is rotated about its pivot pin 29 against the bias of its spring 32, the upper end or tang 33 rotates freely in the radial leg 35 of the L-shaped groove 34 in the presser member.

In the event that the weight applied to the presser member was great enough to break the frangible ring 9, but not great enough to compress the second spring 17 and effect relative movement between the presser member and the firing pin retainer, the presser member and the entire firing assembly 11 will return to normal position as soon as the weight is removed.

When the presser member has been rotated clockwise, as viewed in Fig. 2, tosafe position, the tang 33 of the sear will be held against movement in the leg 36 of the L-shaped groove and the firing pin can not be released from the notch 30. In the event that the mine and fuze have been emplaced with the fuze in safe position, and a. vehicle passes thereover, the presser member 8 and the fuze assembly will descend under the applied weight without change of relative position, because the locked sear prevents downward movement of the cap member 21 and release of the firing pin. The presser member and the fuze assembly will return to safe position under the bias of the first spring 13 regardless of the number of times depressed.

We have thus provided a fuze which is simple, efficient and easily assembled and disassembled without the use of special tools.

While we have disclosed a form of the invention presently preferred by us, various changes and modifications will occur to those skilled in the art after a study of the present disclosure. Hence the disclosure is to be taken in an illustrative rather than a limiting sense; and it is our desire and intention to reserve all modifications falling within the scope of the subjoined claims.

Having now fully disclosed the invention, what we claim and desire to secure by Letters Patent is:

l. A fuze comprising a hollow casing have a closure plate secured in its lower end and stop means in its upper inner end, a presser member normally abutting said stop means and being rotatable therein from a normal to a safe position, a firing assembly slidable in said casing from a normal to a firing position, said assembly comprising a firing pin retainer having an axial bore and an offset recess, a cap member slidable in said bore, there being a coaxial bore in said cap, a firing pin in said coaxial bore formed with a diametrically enlarged head, an unstressed firing spring surrounding said pin and resting on said firing pin head, a pivot element in said firing pin retainer spanning said offset recess, a sear pivoted intermediate its ends about said pivot element and having its upper end extending beyond said firing pin retainer forming a tang, there being a notch in the lower end of said sear engageable with said firing pin head and said sear having a cam surface engageable with the lower end of said cap member in normal position, a first spring member supporting said firing assembly in spaced relationship with said closure plate, and a second spring member supporting said presser member in spaced relationship with said firing pin retainer, said springs being compressible upon depression of said presser member whereby said cap member is depressed to stress said firing pin spring and engage the cam surface to free said firing pin to the bias of the firing spring.

2. A fuze as recited in claim 1, said presser member having a radial groove in its under surface in radial alignment with said tang wherein said tang freely rotates when said sear is cammed from engagement with the head of said firing pin, and an arcuate groove in communication with the radial groove whereby upon rotation of said presser member to safe position the arcuate groove is moved to embrace said tang and hold it against rotation in said offset recess to hold said sear in engagement with said firing pin head.

3. A fuze comprising a cylindrical casing having a longitudinal axis and a coaxial cavity formed with stop means at its upper end, a closure plate secured in the lower end of said casing and having a primer seated therein, a presser member slidable in the upper end of said cavity and having an L-shaped groove therein, a firing pin retainer slidable in said cavity intermediate said presser member and closure plate and having an axial bore, a first spring member in said casing urging said pin retainer away from said closure plate, a second spring member positioned between said pin retainer and presser member urging said presser member against said stop means in normal position, a cap member slidable in the axial bore in said pin retainer and having an axial bore and counterbore therein, a firing pin slidable in said pin retainer bore and having a diametrically enlarged head thereon, a normally unstressed firing pin spring in said pin retainer counterbore and surrounding said pin, and a spring pressed sear pivoted intermediate its length to provide a lower arm having a notch therein to receive the enlarged head of said firing pin and a cam surface restraining downward movement of said cap member in normal position and a tang at its upper end normally positioned in one leg of said L-shaped groove whereby upon clockwise rotation of said pressure member said tang is locked in the other leg of said L-shaped groove for rendering the fuze safe, whereby said presser plate and pin retainer will be depressed without releasing said firing pin.

4. A fuze comprising a cylindrical casing having a longitudinal axis and a coaxial cavity formed with stop means at its upper end, a closure plate secured in the lower end of said casing and having a primer seated therein, a presser member slidable in the upper end of said cavity and having a groove in its under surface, a firing pin retainer slidable in said cavity intermediate said presser member and closure plate and having a coaxial bore, a first spring member urging said pin retainer upwardly from said closure plate, a second spring member positioned between said pin retainer and presser member urging said presser member against said stop means in normal position, a cap member slidable in the axial bore in said pin retainer and having a coaxial bore and counterbore therein, a firing pin slidable in said pin retainer bore and having a diametrically enlarged head thereon, a normally unstressed firing pin spring in said pin retainer counterbore surrounding said pin and resting on said pin enlargement, and a spring pressed sear pivoted intermediate its length to provide an upstanding tang movable in the groove in said presser member and a lower arm having a notch therein to restrain the enlarged head of said firing pin and a cam surface restraining downward movement of said cap member in normal position whereby on depression of said presser member and pin retainer said cap member is forced downwardly to first compress said unstressed firing pin spring and later cam said sear outwardly to release said firing pin to strike said primer under the bias of said compressed spring.

5. A fuze comprising a hollow casing having a longitudinal axis, a presser member axially slidable in the upper end of said hollow casing and having a radial groove in its lower surface and an arcuate groove concentric with said axis and in communication with the radial groove, a closure plate secured in the lower end of said casing and having a primer seated therein, a firing pin retainer having a coaxial bore and being slidable in said casing with said presser member from normal to firing position, a first helical spring member in said casing resiliently supporting said pin retainer in spaced relationship with said closure plate and primer in normal position, a second helical spring in said casing resiliently supporting said presser member in spaced relationship above said pin retainer in normal position, a cap member slidable in the coaxial bore in said pin retainer and having an axial bore and counterbore forming a shoulder at the upper end of the counterbore, a firing pin slidable in the bore of said cap and having a diametrically enlarged head slidable in the pin retainer bore, a normally unstressed firing pin spring surrounding said pin and positioned in said counterbore between said shoulder and head, and a sear pivoted in said firing pin retainer intermediate its ends in substantial parallelism with said longitudinal axis, said sear having a tang formed on its upper end and a notch in its lower end to engage the enlarged head of said pin in normal position, there being a cam face on said sear adjacent said notch in the path of axial movement of said cap member whereby when pressure is applied to said presser member downward movement thereof simultaneously with said pin retainer and second spring member against the bias of said first spring member causes said pin retainer to abut said closure member, con tinued downward movement of said presser member forces said cap member downwardly compressing said path of movement of said cap member to release the enlarged head of said firing pin to the bias of said firing pin spring thereby detonating said primer, said presser member, being rotatable about said longitudinal axis whereby said tang is movable radially in said radial slot in normal position and locked in said concentric slot in safe position when said presser member is rotated clockwise.

References Cited in the file of this patent UNITED STATES PATENTS Walker May 18, 1954 FOREIGN PATENTS Germany Nov. 28, 1932 

